The Mammoth property is located at elevations of 1400 to 1750 metres at the head of Arison (Buffalo) Creek, 4.8 kilometres east of Silverton. The Standard mine (082FNW180) lies about 1.6 kilometres to the west. The underground workings are mostly on the Mammoth and Monarch claims.

The showing was discovered and staked in May 1921. Five claims, the Monarch, Mammoth, Moose, Highore, and Hercules (Lots 13571-13575 respectively were subsequently Crown-granted. Owners H.V. Dewes, S. Wetterhouse, and associates optioned the property in 1922 to Standard Silver-Lead Mining Co., of Spokane. A total of 171 metres of underground development was carried out before the option was given up in 1923. The owners resumed work on the property the following year. R.A. Grimes obtained an option on the property and in June 1926 re-optioned to The Porcupine Goldfields Development & Finance Company, Limited. Exploration and development work continued into 1927 when the option was given up. Western Exploration Company, Limited acquired an option on the property from Grimes in 1928. During 1929 a 4877-metre aerial tramline was installed to connect the No. 7 level with a 100 ton-per-day flotation mill installed at Silverton on the shore of Slocan Lake. The equipment was given a trial run early in 1930 and the mine was shut down later in the year pending better metal prices. Lessees carried out small scale mining operations during 1932-34. The company resumed work in 1935 and the mill operated from July 1935 until March 1936, and again from the spring of 1937 until December 1937.

Following a period of inactivity when company attention was directed to reopening the Standard and reclaiming tailings from Slocan Lake, the mine again came into production in 1942. By 1944 the orebody between Nos. 7 and 5 levels was mined out, and a considerable amount of exploratory drilling was done, much of it below No. 7. In the same year a new adit, the Monarch, was started to investigate intersections obtained by surface drilling. All work ceased in May 1945. The company began driving No. 9 level in September 1948. The aerial tramway was rehabilitated in 1950 and the mill operated from November of that year until November 1952. During 1954-55 the No. 7 level was extended westerly through the Monarch claim into the Hecla zone (082FNW062) of the Standard property. Production from the Mammoth resumed in 1956. During 1958-59 the No. 12 crosscut adit was driven 792 metres to the downward extension of the Mammoth zone. The adit for the most part parallels, and in two places cuts the vein on the adjacent Buffalo property (082FNW182). Work ceased in June 1959.

Loma Minerals Ltd. acquired a lease on the property and carried out development work from February 1961 until October 1962. Johnsby Mines Limited was incorporated in November 1962 to operate the property under the terms of an agreement between the owner, Western Exploration, and Rayrock Mines Limited and Faraday Uranium Mines Limited. Development work began in a new exploration adit on the Standard property. Mining began on the Mammoth between 9 and 12 levels in 1965 and continued until the ore was exhausted late in 1966. Total development work to that date is estimated at approximately 2560 metres of drifts and crosscuts in 6 adits, Nos. 1, 2, 4, 7, 9, and 12, and 6 intermediate levels. No. 3 1/2 and two other short adits lie to the west of the main orebody, and an exploratory cross-cut, the 152-metre long Monarch adit, lies farther to the west.

Arjan Pacific Ltd. by an agreement dated September 26, 1973 purchased the Mammoth and adjacent properties from Western Exploration Company, Limited. In 1976 the Mammoth and Buffalo properties were owned by D.W. Pengelly, of Silverton.

Regionally, the area lies on the western margin of the Kootenay Arc, in allochthonous rocks of the Quesnel Terrane. In the vicinity of the occurrence, the Quesnel Terrane is dominated by very fine grained clastic sedimentary rocks of the Upper Triassic Slocan Group that include locally weakly metamorphosed argillite, quartzite, limestone and some tuffaceous rocks. These sedimentary rocks are intruded by dikes, sills and stocks of varied composition and origin. Permian and/or Triassic Kaslo Group metamorphosed volcanic rocks occur to the north of the Slocan Group rocks. Middle Jurassic Nelson intrusions are immediately south of the Slocan Group and are inferred to be the source of granitic to pegmatitic sills and dikes found in the area. The Nelson intrusions comprise at least six texturally and compositionally distinct phases ranging from diorite to lamprophyre. The most dominant phase is a medium to coarse grained potassium feldspar porphyritic granite (Paper 1989-5).

The Mammoth occurrence is hosted by various, more or less calcareous, mostly massive argillites and quartzites of the Slocan Group intruded by various sills and dikes of feldspar porphyry and bodies of hornblende or quartz diorite related to Nelson intrusions. Although deformation is intense, the rocks are generally flat lying in the immediate area of the mine.

The deposit occurs within an oblique, normal and sinistral shear zone up to 15 metres wide with displacement probably in the order of 100 metres. The mineralized vein has been developed from five main adits over a vertical range of 300 metres on the Mammoth claim and at least one crosscut adit on the Monarch claim. The orebody is pipe-shaped and appears to have a 20 degree plunge to the southeast. Above the No. 5 level it divides into two tabular masses in a comparatively straight fissure that strikes 075 degrees and dips 40 to 65 degrees southeast. On the No. 8 level the Buffalo (082FNW182) vein intersects and merges with the Mammoth vein. The Mammoth vein is believed to continue to the west and correlate with the "I vein" on the Standard property (082FNW180).

Within the mine mineralization was fairly continuous over a length of 130 metres and consisted of streaks, bands, lenses and disseminations of ore and gangue associated with abundant brecciated wallrocks. The ore occurred in massive lenses 1 to 1.5 metres wide and consisted of coarse to fine grained cubic and sheared galena with coarsely cleavable masses of sphalerite and minor tetrahedrite. Mineralization was more common at the footwall of the shear zone but was also observed at the hangingwall as well as in irregularly dispersed masses within the shear zone. The ore minerals occurred with coarse calcite, siderite and minor quartz. Deformation subsequent to mineralization resulted in the fracturing of sphalerite and to the development of a well defined gneissic structure in which galena has flowed around and surrounded fragments of sphalerite.

Complete production figures are not available because the Mammoth mine ore was jointly milled with that from the Standard (082FNW180) and Enterprise (082FNW148) properties prior to 1958, and Hecla (082FNW062) property after 1964. However, production from the Mammoth mine between 1925 and 1980 yielded about 25 tonnes of silver, 2622 tonnes of lead, 4158 tonnes of zinc, 20 tonnes of cadmium, 46 kilograms of copper and 3 kilograms of gold from 63,865 tonnes mined.